This invention concerns lighting glass, i.e., glass for bulbs for automobiles and bulbs for household use, capable of transmitting light of a predetermined chromaticity (orange to red) required for directional indicator lamps or tail/stop lamps, for example, in automobiles, and which does not contain deleterious ingredients such as lead, cadmium, selenium, chromium and arsenic, and a colored glass bulb using the above-mentioned glass, as well as a manufacturing method thereof.
It is required for lamps and lamp units used, for example, in direction indicators or tail/stop lamps of automobiles that they have specified chromaticity (orange and red) determined in accordance with standards of the International Electric Standard Conference (IEC) or Japanese Industrial Standards (JIS). For example, as lamp units for automobile direction indicators, those transmitting light having predetermined chromaticity by the combination of bulbs using colorless transparent glass and plastic covers of orange color have been adopted so far. In the same manner, those comprising bulbs using colorless transparent glass and plastic covers of red color in combination have also been adopted for tail/stop lamp units. However, the groups of lamp units located at front and rear portions of automobiles also require transparent plastic covers for head lights and back lights in addition to covers of red and orange colors, and the step of assembling them is complicated and they are expensive in view of the number of parts.
In view of the above, a bulb using glass which itself is colored orange (colored glass) or a bulb in which a orange coating agent is coated on the surface of the glass bulb in combination with a colorless transparent lens cover (lamp unit) has been adopted recently for lamp units of direction indicators. Further, also in tail/stop lamp units, lamp units using a light emitting diode that emits red color as a light source in combination with a colorless transparent plastic cover have been recently provided.
Thus, the number of parts is decreased and the cost is reduced, particularly, with respect to direction indicator lamp units. In addition, such a countermeasure has been evaluated also in view of design in situations where the types of automobiles become more versatile. However, orange colored glass used currently for lamps for use in direction indicators contains cadmium or selenium which is designated as an environment hazardous substance, for which saving or inhibition of use has taken place all over the world. Further, electric bulbs coated with coating agents on glass sometimes contain a deleterious Pbxe2x80x94Cr (lead-chromium) colorant in the coating agent. Further, they also involve problems of color speckles caused by coating speckles in the coating step, thermal discoloration and peeling. Further, while recycling is possible for colorless transparent glass or colored glass by nature, it is difficult when the coating is applied.
On the other hand, in the tail/stop lamp units, in a case where colorless transparent plastic covers are used for red emitting diodes, since more than ten of the light emitting diodes are required per one lamp, this increases the number of parts and makes the assembling step further complicated, and results in the problem that the cost is increased. Further, in a case of using colored glass, a red colored glass using cadmium-selenium for the colorant may be considered but it is not preferable in view of the same environmental concerns as described above. Further, while copper may sometimes be used as a colorant, since it requires an extended heat treatment after the molding of the bulb in order to obtain a predetermined chromaticity, such bulbs have not yet been popularized generally in view of availability and cost and only a limited number of them is marketed at present. Further, while electric bulbs in which a coating agent is coated on glass by the same method as in the direction indicators are marketed only limitedly, they not only involve the same problems but also can not satisfy the standards for the red color required for automobile bulbs specified according to JIS or the like.
While it has been known so far that red colored glass can be obtained by generating a colloid comprising SbS2 or SbS3 in glass, lighting glass using such colored glass has not yet been put to practical use.
One of the reasons is that either an excessive or insufficient amount of Sb in the glass causes a problem of turbidity and no appropriate content has yet been determined.
As another reason, only glass from transparent to yellow can be obtained by rapid cooling from a temperature greatly exceeding the softening point (900 to 1000xc2x0 C.) usually used in the molding of a glass tube or bulb, so that a re-heating treatment has to be applied in order to obtain red or orange colored glass. However, since the coloring temperature range upon re-heating treatment is not below the softening point, it also results in a problem of deformation of molded glass.
The present invention has been accomplished in view of the foregoing situations and provides lighting glass which does not contain deleterious ingredients such as lead, cadmium, selenium, chromium and arsenic and which can be manufactured in a relatively short period of time, and a colored glass bulb, and a manufacturing method thereof.
As a result of an earnest study, the present inventors have found that lighting glass of various warm colors can be obtained by incorporating an appropriate amount of Sb and, further, an appropriate amount of S in glass and generating a colloid comprising SbS2 and/or Sb2S3.
Further, it has been found that lighting glass of various warm colors can be obtained by incorporating appropriate amounts of Sb and S into glass and applying a re-heating treatment while controlling the temperature and the time thereby generating a colloid comprising SbS2 and/or Sb2S3. In the re-heating treatment, it has been found that red lighting glass is obtained when rapid cooling is conducted after the re-heating and orange lighting glass can be obtained when cooling at a predetermined temperature gradient without rapid cooling is conducted.
Further, it has also been found that with respect to lighting glass to which a re-heating treatment has been applied for obtaining the red coloration, even when the color is changed to a red-orange color (an intermediate color between red and orange, specified according to IEC standards or JIS) by heat (flame) in a subsequent fabrication, it can easily regain a desired red color with no deformation by an additional re-heating treatment at a temperature lower than the softening point of the glass and at a temperature lower than that used for the original re-heating treatment.
That is, this invention provides a lighting glass in which 0.3 to 1.0% by weight of Sb calculated as Sb2O3 and 0.5 to 1.0% by weight of S calculated as SO3 are contained in a SiO2xe2x80x94Al2O3xe2x80x94R1Oxe2x80x94R22O-based glass (where R1 represents Ca, Sr, Mg and Ba and R2 represents Na, K and Li), and a colloid comprising SbS2 and/or Sb2S3 is generated in the glass.
The SiO2xe2x80x94Al2O3xe2x80x94R1Oxe2x80x94R22O-based glass (where R1 represents Ca, Sr, Mg and Ba and R2 represents Na, K and Li) preferably has a composition comprising on a weight % basis, SiO2: 60 to 75%, Al2O3: 1 to 5%, B2O3: 0 to 3%, BaO: 0 to 10%, SrO: 0 to 12%, CaO: 0 to 18%, MgO: 0 to 5%, Na2O: 1 to 17%, K2O: 1 to 17% and Li2O: 0 to 3%. The lighting glass according to this invention can be used suitably for colored glass bulbs.
Further, this invention provides a method of manufacturing lighting glass of a SiO2xe2x80x94Al2O3xe2x80x94R1Oxe2x80x94R22O-based glass (where R1 represents Ca, Sr, Mg and Ba and R2 represents Na, K and Li) in which 0.3 to 1.0% by weight of Sb calculated as Sb2O3 and 0.5 to 1.0% by weight of S calculated as SO3 are contained, wherein a re-heating treatment is applied after molding by heat melting. The SiO2xe2x80x94Al2O3xe2x80x94R1Oxe2x80x94R22O-based glass (where R1 represents Ca, Sr, Mg and Ba and R2 represents Na, K and Li) preferably has a composition comprising on a weight % basis, SiO2: 60 to 75%, Al2O3: 1 to 5%, B2O3: 0 to 3%, BaO: 0 to 10%, SrO: 0 to 12%, CaO: 0 to 18%, MgO: 0 to 5%, Na2O: 1 to 17%, K2O: 1 to 17% and Li2O: 0 to 3%. Further, the re-heating treatment is conducted, preferably, at a temperature of from 650 to 750xc2x0 C. More specifically, it is preferred to apply the re-heating treatment to the molded glass at 650 to 700xc2x0 C. for 3 to 30 min followed by rapid cooling by leaving the re-heated glass at a normal temperature or applying a re-heating treatment at 680 to 700xc2x0 C. for 1 to 3 min and then gradually cooling down to a normal temperature at a rate of 3 to 10 sec per 1xc2x0 C. Heating times of greater than 30 min are possible but are not practical.
Further, this invention concerns a method of manufacturing lighting glass, wherein after the re-heating treatment, an additional re-heating treatment is applied at a temperature lower than the temperature for the original re-heating. The temperature for the additional re-heating treatment is preferably 550 to 600xc2x0 C.
The manufacturing method of lighting glass according to this invention can be used suitably to manufacture colored glass bulbs.